Booster-type servomotor for brake systems



Jan. 8, 1963 G. T. RANDOL BOOSTER-TYPE sERvoMoToR FOR BRAKE SYSTEMS ...WNS Nubt Oh J 8 Sheets-Sheet `1 nm. t w ...f

Original Filed Sept. 2. 1958 Jan. 8, 1963 G. T. RANDoL 3,072,106

BOOSTER-TYPE SERVOMOTOR FOR BRAKE SYSTEMS l Original Filed Sept. 2. 1958 8 Sheets-Sheet 2 Jan. 8, 1963 G. T, RANDOL 3,072,106

BOOSTER-TYPE SERVOMOTOR FOR yBRAKE! SYSTEMS Original Filed Sept. 2, 1958 8 Sheets-Sheet 3 FIG.. 3.

Jan. 8, 1963 G. T. RANDOL BOOSTER-TYPE SERVOMOI'OR FOR BRAKE SYSTEMS Original Filed Sept. 2, 1958 8 Sheets-Sheet 4 111 08 G "8147 126 14a 6A Il f cv .105 if; e

Q15, gg; 159 ZO 762 FIG. 8. 96 48 50 .55,95 56 102 197 VMZ 799 Jan. 8, 1963 vG. T. RANDOL 3,072,106'

BOOSTER-TYPE SERVOMGTOR FOR. BRAKE SYSTEMS Original Filed Sept. -2, 1958 8 Sheets-Sheet 5 FIC-1-9.

Original Filed Sept. 2, 1958 Jan. 8, 1963 vll G. T. RANDOL BOOSTER-TYPE SERVOMOTUR FOR BRAKE SYSTEMS 8 Sheets-Sheet 6 50a G. T. RANDOL 3,072,106

BOOSTER-TYPE SERVOMOTOR FOR BRAKE SYSTEMS Original Filed Sept. 1958 Jan. 8, 1963 8 Sheets-Sheet 7 web. 4,7b

Jan. 8, 1963 G. T. RANDOL 3,072,106

BOOSTER-TYPE sERvoMoToR FOR BRAKE SYSTEMS y 7215 mab nited States 3,072,106 BDSTER-TYPE SERVOMOTQR FR BRAKE SYSTEMS Glenn T. Randol, 2nd Ave. and Paull St., R0. Box 275, Mountain Lake Park, Md. Continuation of abandoned application Ser., No. 758,405, Sept. 2, 1958. This application July 5, Het, Ser. No.

2z Claims. (ci. tzr- 41) This application is a continuation of my copending application Serial No. 758,405, tiled September 2, i958, now abandoned.

The present invention relates to booster-type servomotors adapted for use on automotive vehicles and the like, and particularly to a novel and improved servomotor in operative association with the conventional master cylinder of hydraulic brake systems on such vehicles, said invention constituting an improvement on the servomotor disclosed in my earlier application Serial No. 684,946, iiled September 19, 1957.

In my copending application referred to, there is disclosed a simple, low-cost and self-contained control valve construction which is movably supported as a unit directly on the casing of the vacuurn-power servomotor and independently of the power assembly movable in said casing, whereby rigid coaxial disposition of the power assembly and control valve therefor is eliminated to avoid precision alignment thereof with bearing supports provided on the casing were the control valve and power assembly integrated as in prior art apparatus of this general character. In this manner, numerous machining operations are dispensed with, and the assembly and servicing of the control valve is greatly facilitated, and more economically too, since the power assembly and control valve therefor are separate unitary components permitting either of them to be inspected or serviced independently of the other.

The control valve referred to in the object next above comprises at least two principal cooperating elements disclosed herein as a valve sleeve and a valve piston therein relatively displaceable from normal disposition wherein pressures are balanced on opposite sides of the power assembly for power-inactivation of the servomotor, to operating on position to establish differential pressures on opposite sides of the power assembly for power-activation of the servomotor, said control valve preferably including a normally preloaded spring to bias the said valve elements apart to normal disposition, in one embodiment of the invention as will appear.

In my above-identied earlier application Serial No. 684,946, there is also disclosed reaction spring means having a helically formed expansion spring which is normally preloaded to supply reaction to pedal depression as a measure of the total braking force effective at different stations of pedal movement. This reactive spring is operably disposed within the vacuum-power chamber of the motor and encircles a portion of a work-performing element actuated by the power member with one end of said spring bearing on the inside of the front end wall of the power cylinder and the other end reacting on a cup-shaped spring seat relatively slidable with respect to said work element and normally engaging the power member to return it to normal position under influence of said reactive spring, said spring reacting continuously on the control valve element actuated by the brakepedal whereby depressing the pedal moves this valve element and spring seat simultaneously relatively to another control valve element telescopically associated with the pedal-actuated element and movable in unison with the power member, to isolate the atmosphere from and place the vacuum source in communication with the rtf@ :sul

vacuum-power chamber and thus energize the power member.

ln the reduction oi this novel spring reaction principle to commercial use, it was found that while this type of reaction provides the operator with highly satisfactory control during initial slack take-up movement of the pedal up to an initially pressurized condition of the brake fluid insufficient to produce a lirm braking effect as delined by the thrust-transmitting capacity of the control valve return spring, but at the point where the power phase is introduced to pressurize the brake fluid to render the braking action firmly effective, movement of the power member and associated fluid-displacing parts including the spring seat aforesaid induces a substantially arrested status of said operating components with consequent negation, of further increasing reaction from the reaction spring aforesaid notwithstanding pressure on the brake fluid under inuence of the power member continues to build up by virtue of increasing the vacuum opening in the control valve. Consequently, the operator continues to receive the same reaction as was effective at the beginning or" the power phase which tended to produce a discernible power-surge on the pedal for lack of increasing reaction from the reactive spring which depends on movement of its spring seat to produce its reactive eitect.

A further disadvantage found in the aforesaid reactive spring per se is that a heavily rated spring is required to smooth out the mergence of the power force with initial operator force to prevent possible power-surge at this point in the braking application which increases pedal-load to the extent that such spring reaction alone does not provide the reduced operator for-ce normally associated with power-boosted brakes, and too, since this spring must be under tension in response to pedal movement by the operator, at certain stages of the braking application, a wave-surge etect is transmitted to the operators foot as the pedal literally iioats on this spring during the working stroke of the power-booster to pressurize the brake tluid.

lt is thus seen from the foregoing discussion of my earlier disclosure Serial No. 684,946 that use of spring action alone as a reactive force on the operator pedal is inadequate through the fluid pressurizing phase of the power-booster, serving only to provide increasing resistance to pedal movement during the slack take-up movement of the pedal to the point of initially actuating the work-load, and thereafter the reactive torce from this spring becomes substantially a constant force in relation to power-boost actuation of the work-load, due to substantially stationary condition of the workperforming element under power-booster actuation, and as a consequence, a possible power-surge can occur as the booster force is introduced upon increase of pressure on the pedal.

To overcome the above noted disadvantages and thus provide smoothly increasing resistance on the pedal as the pressure on the brake fluid builds up under iniluence of the powerbooster for predictable brake-control, with such increasing resistance being effective at any given position of the pedal up to the point of power-run-out, the present invention seeks as a primary object to preferably utilize a two-lever mechanical reaction mechanism of new and improved construction and operation between the work element and power member, and which includes a tulcrum block for varying the division of work between Vthe driver and booster unit by changing the height of said block, said work element being capable of direct actuation by said power member, the reaction mechanism comprises said two levers individually offset radically from the axis of the power member, and optionally, said levers may be arranged in an interconnected circular configuration to form a reaction member such as a disc. The individual levers are characterized by rigidity to transmit proportional reaction ou said work-performing element to the brake-pedal, while the reaction disc member is characterized by resiliency to provide a progressively increasing reaction on said brake-pedal. The aforesaid reactive spring and the lever reaction mechanism combine to produce a two-stage transfcral of reaction to the pedal, the former providing instant opposition to initial pedal movement, while the latter impresses a proportional reactive force from the master cylinder (workload) via said work element against the pedal, and wherein said reaction levers are ineffective to transmit reaction in their normal disposition, and operable to reactiontransmitting disposition under operator-actuation of said one valve element, operation of said levers to transmitting disposition being effective to axially separate said power member and work performing element to condition said reaction levers to transmit reaction from the master cylinder (work-load) accompanied by relative displacement of the control valve to operating on disposition, as a function of the reaction on said work-performing element.

A further salient feature of my invention resides in the provision of new and improved auxiliary or vacuum relief valve means operably incorporated in the power member for venting the vacuum-power chamber to atmosphere via the atmospheric chamber of the booster motor in cooperation with the restricted air-vacuum control opening in the main control valve to enable rapid release of the power member irrespective of the mode of pedal manipulation so that brake release keeps pace with the rate of withdrawal of foot pressure from the pedal.

A modified reaction device installation is provided wherein the lever-action of the resilient diaphragm or disc is eliminated, said disc being constructed similarly to the disc having lever-action but with its marginal portion which encircles its central aperture, fixed on the work-performing element or push-rod actuated by the power member of the vacuum-motor whereby pressure applied to its peripheral marginal portion via the aforesaid spring seat moved by the operator, develops tension in the disc from its normally relaxed status to provide increasing resistance to brake-pedal depression in direct proportion to the distance the pedal is depressed as a measure of the braking force being applied at any given position along the full operating stroke of the pedal, the normally relaxed status of the disc or when subjected to slight tension, performs the function of moving the power-actuated assembly and work-performing element simultaneously in cooperation with the control Valve return spring under normal preload until a predetermined reaction becomes eective, at which point, the reaction from the work element becomes substantially constant while the booster motor is energized to actuate said work element to render the work-load provided by the master cylinder effective as required. This initial operation of the work element usually opposed by a normally preloaded spring, is brought about with assistance from the normally preloaded status of the aforesaid return spring normally separating the control valve parts to shutoff the Vacuum from the vacuum-power chamber.

A further important object of my invention is to provide such novel reactive disc installed normally relaxed, therefore devoid of tension, or said disc may be optionally installed normally under predetermined tension insuliicient to overcome spring-action against the workperforming element, such spring-action serving in part `as the return means therefor. This latter arrangement, however, being applicable to the first embodiment only wherein the disc is characterized by combined tension and lever-action for transmitting progressive reaction from the work-performing element to the brake-pedal; but in the disc installation described in the object immediately preceding, the predetermined tension may be varied at will.

Another modication of my invention provides a new and improved lever-reaction system or mechanism which is devoid of resiliency characterizing the aforesaid reaction diaphragm, and which provides reaction on the operator member Via the control valve element acted on by said member proportional to the force developed by the vacuum-motor. This novel lever-reaction system replaces the resilient diaphragm or disc employed in either of the embodiments previously described.

An object relating to the object next preceding is the provision of new and improved means for conditioning the reactive-lever mechanism to transmit reaction forces from the work-performing element to the operator member in response to initial movement of the operator member from its normally released position to take up the slack, for example, in the hydraulic brake system to a point of sufficiently pressurizing the brake fluid to render the Huid-displacing unit substantially stationary to induce operative energization of the vacuum-motor.

My invention further provides an optional feature in the way of a novel mechanical connection between the control valve piston and power member of the vacuumbooster whereby the valve piston and power member have axial movement in unison while limited radial movement relatively therebetween is provided to prevent binding and/or wear on the operating parts which could result from possible slight disalignment. Thus, this connection eliminates need for critical tolerances to maintain coaxial exactness between the power member and control valve therefor and, for example, with respect to the piston in a hydraulic master cylinder which constitutes part of the work-load, since the movable assemblies aforesaid are capable of limited lateral displacement withrespect to each other without hindering their free axial movement. Another advantage provided by this novel mechanical connection is that the spring utilized to separate the control valve sleeve and piston to normal off disposition wherein the vacuum is cut-oit from the power chamber, may be eliminated since the control valve element actuated by the brake-pedal is opposed by the reactive helical spring aforesaid, and the other valve element moves in follow-up engaged relationship with the power member opposed by the spring reacting on the work-performing element, and the resilient disc member if the latter is utilized as the reaction member. Accordingly, if the valve element separating spring is eliminated, the servomotor becomes energized to assist in operating the work-performing element as a consequence of the reaction of the spring opposing movement of the work-performing element, while if a valve separating spring is employed of such preloaded magnitude that the spring reacting on the work element can be overcome, then the servomotor becomes energized to assist in operating the work element upon the latter encountering a work-load suflicicnt to create reaction of such magnitude as to induce the valve separating spring to yield and thereby accommodate relative displacement of the valve elements to operating on position for poweractivation of the servomotor.

With these and other objects and advantages in view, the invention consists of the new and novel combinations, construction, and arrangement of parts as hereinafter more fully described, set forth in the claims appended hereto, and disclosed in the accompanying drawings forming a part hereof, wherein:

FIGURE 1 is a longitudinal Vertical section of a booster brake mechanism embodying my invention, and exemplarily shown connected to operate the master cylinder of a hydraulic brake system conventionally employed on automotive vehicles or the like, and wherein the vehicle brakes are fully released;

FIGURE 1A is a longitudinalsection of a portion of FIGURE 1 showing details of the residual pressure check.-

valve associated with the discharge port of the master cylinder;

FIGURE 1B is an enlarged sectional view of a portion of FIGURE l showing details of the air filter device;

FIGURE 2 is a longitudinal vertical section of a portion of FIGURE l on an enlarged scale of the mechanism per se with certain parts shown in elevation;

FIGURE 3 is a transverse sectional View taken on a reduced scale along the line 3-3 of FIGURE 2, and showing details of the novel reaction device associated with the operator-operated means;

FIGURE 4 is another transverse sectional view taken on a reduced scale along the line 4--4 of FIGURE 2, and showing details of the control Valve structure and associated exible conduit connections to the exterior of the vacuum-motor cylinder and to the power chamber thereof via the power member movable in said cylinder;

FIGURE 5 is a fragmentary sectional view taken along7 the line 5 5 of FIGURE 4 on an enlarged scale and showing details of the air-vacuum ltting mounted on the power member;

FIGURE 6 is a longitudinal vertical section similar to FIGURE 2 on substantially the same scale showing the parts moved to their relative operating positions corresponding to inauguration of energization of the vacuum motor to assist in pressurizing the fluid in the master cylinder;

FIG. 7 is a fragmentary sectional view of FIGURE 2 showing the vacuum relief valve on an enlarged scale for clarity of detail;

FIGURE 8 is a fragmentary sectional view of FIGURE 6 showing the vacuum relief valve on the same scale as FIGURE 7 for clarity of detail;

FIGURE 9 is a face view on an enlarged scale of the resilient reaction disc per se in the novel reaction device;

FIGURES 9A, 9B, 9C, 9D, and 9E are variations in the construction of the spring-disc per se illustrated in FIGURE 9;

FIGURE IG is a longitudinal vertical section of a modified form of the novel reaction device in which the leveraction is eliminated whereby reaction on the operatoroperated member is resilient only and in direct proportion to the distance said member is moved from its normal released position;

FIGURE ll is an operated depiction of the FIGURE l modification wherein the power phase is in readiness to be inaugurated;

FIGURE l2 is another modification of my invention shown in longitudinal vertical section wherein a new and novel lever-reaction system or mechanism devoid of resiliency which characterizes the reaction device aforesaid, is depicted and which transmits the force developed by the vacuum-motor proportionally to the operator member via the control valve sleeve;

FIGURE 13 is a transverse sectional view taken along the line ITG-I3 of FIGURE l2 modification;

FIGURE l4 is an operated depiction of the FIGURE 12 modification wherein the power phase is in readiness to be inaugurated;

FIGURE l illustrates a further modification of my invention wherein the control valve piston is mechanically coupled to the vacuum-motor power member for axial movement as a unit, said coupling accommodating relative radial displacement of these two components; and

FIGURE 16 is a transverse sectional view of FIGURE l5 taken along the line IIS-d6 thereof to show further details of the mechanical coupling arrangement between the valve piston and power member.

Like characters ot" reference designate like parts and assemblies thereof, in the several views with like parts and assemblies in the modified forms of the invention being distinguished, however, by the suffixes 11, b, and c etc. respectively to each.

Referring now to the drawings, and particularly to FIGURES l, 2, 3, 4 and 5 my improved booster brake mechanism generally designated BM comprises: a fluidpressure actuated servomotor or more specifically a vacuum-operated motor or power cylinder generally designated VM, in operative association, for example, with the conventional hydraulic master cylinder MC having an integral end flange l@ for mounting it on end wall it of the vacuum-power motor as by an adapter plate 12 secured thereto by a plurality of headed bolts I4, preferably four in number, which project from the inside of the wall II through suitable registering holes in said wall and plate respectively, thence through holes 15 in the marrinal portions of the flange In'. Lock nuts I6 are threaded onto the bolts to secure the end plate tightly against the vacuum motor end wall to provide a unitary assembly thereof. The headed ends of said bolts are rigidly attached as by presst or welding to the inner side of the end wall II. Sealing gaskets are provided between the faces of the ange Id and adapter plate and between the latter and the confronting face of the end wall Il?. to effect an airtight assembly thereof. The master cylinder MC has the usual Huid-displacing assembly or unit comprising: the spool-type piston 2t), residual pressure valve RV and a spring-loaded one-way pressure discharge valve 22 (see FIGURE 1A) associated with the discharge port 23, the latter serving to transmit uid under pressure from the working chamber 24 into the hydraulic lines and wheel cylinders (not shown) to operate, for example, the wheel brakes (not shown) of a motor vehicle or the like, and a piston return spring 25 is operably disposed in the working chamber 24, which also serves to control the residual pressure valve RV. A gravity-type reservoir 26 is disposed above the working chamber and communicates therewith via the compensating and intake ports 27, 2S respectively, and passageways 29 in the head of said piston, to prevent cavitation in the working chamber 2.4 by maintaining it lled at all times, said piston being equipped with the cupshaped pliant head seal 33t and the fluid-retaining seal 32 to prevent Huid loss past the piston to the exterior when the latter is actuated to pressurize the fluid in the working chamber. An integral hub portion 33 projects rearwardly from the ange Titi through coaxial openings in the central portions of the adapter plate, gaskets, and end wail II of the vacuum motor aforesaid, said hub serving to stabilize the master cylinder MC in coaxial disposition with respect to the vacuum cylinder VM.

The rear or opposite end wall 34 of the vacuum cylinder VM is preferably spaced, for example, from the forward side of the firewall FW of the motor vehicle, the latter serving to support the booster brake mechanism BM in operating position in installations operated by a suspended-type pedal mechanism generally designated P and comprising: a pedal arm 35 pivotally suspended at its upper end on the vehicle at 3,45, and the lower end of said arm terminates in a foot pad 37 whereby the operator may exert effort on the pedal mechanism P to operate the same. The outer end of a push rod FR is pivotally connected at 33 to an intermediate point on the pedal arm to control the vacuum motor VM as will appear. Attached to the exterior of the rear wall 34 is a bracket generally designated BR for mounting the booster brake mechanism BM on the firewall in spaced relation thereto best demonstrated in FIGURE l, said bracket being identical in construction and installation to that shown in my earlier US. application Serial No. 684,946 and reference may be had to this disclosure for structural details of this bracket.

The vacuum-power cylinder VM is preferably a differential air-pressure operated motor which utilizes either vacuum or super-atmospheric pressure to create the differential pressures across the movable power assembly PA aforesaid to operatively energize the same. In ordinary automotive installations, a vacuum operated motor is preferred to one operated by compressed air since the engine intake-manifold may serve as the vacuum Source without power loss from the engine.

The vacuum cylinder comprises: a pair of cylindrical cup-shaped casings (shells) Lid, di closed at their` outer ends by said walls ll, 34 respectively, and having their confronting open ends formed with outturned annular flanges d2, i3 respectively, the latter being provided with a plurality of registering holes 44 therethrough in circumferentially spaced relationship.

The movable power assembly PA, which is referred to elsewhere in this specification and in certain of the claims as a pressure-responsive movable wall or unit, power-diaphragm, power-piston or member, provides with the inside of the end wall il on which the master cylinder MC is mounted, a variable pressure or vacuum charnber 45, and the space between the opposite side thereof and wall 3d defines a constant pressure or atmospheric chamber 46, said power assembly comprising: a pair of cup-shaped juxtapositioned plates d'7, 4S mounted backto-back with plate A4i7 having a coaxial central circular opening at d, with their outer peripheral marginal portions iianged oppositely at Sti. A ring-like iieXible powerdiaphragm generally designated D is provided with inner and outer peripheral marginal portions 5l, 52 respectively with the inner portion disposed between the backs of the plates 47, 43 and the outer portion provided with holes in registry with the holes i4 in the iianges 4Z, 43 and disposed therebetween to anchor the diaphragm to the inner side of the vacuum cylinder at the diverging juncture of the two casings aforesaid in airtight sealed relation when the casings and diaphragm are assembled, for example, as by clamping bolts 53 inserted through the holes 54 and drawn tight with nuts to provide a rigid unitary assembly of the two casings as shown. The inner peripheral portions of said diaphragm D and plates 47, i8 are clamped in airtight sealed relation between a forward circular thrust plate 55, and a rearward smaller circular plate 5d, by an inner and outer set of fasteners such as, for example, rivets 57 and S7 respectively and arranged as shown in FlGURES l, 3 and 4. A circular spacer plate 5S is disposed in the openings 49 between the plates 55, 56 and is provided with a plurality of holes et) preferably four in number adjacent its periphery in circumferentially equally spaced relation Which are fitted with pliant ring seals dll of the concentric double-lip type. Pour holes 62 are provided through each of the plates 55, 5d of smaller diameter than holes 6l) in coaxial disposition with respect thereto through which actuatable pins 6d slidably project via said seals 61. The pins 64 are provided with heads 65 tapered inwardly on their underside adjacent the body of the pins to normally engage complemental countersinks 66 which terminate the holes 62 in the thrust plate 55 to insure the power chamber #i5 is sealed against leaks past the pins 64 when in released position notwithstanding the power assembly may be in an operating position, said seals 61 preventing leaks past the body of the pins when the latter are actuated during power assistance as will appear. A central circular opening dit is provided in the plate 56 to be later referred to.

A force-transmitting pilot member or stern generally designated 70 having a medially disposed external annular flange or shoulder 7l fixed coaxially adjacent the forward side of the thrust plate 55 as by welding the right end extension 72 of the stem in a centrally disposed hole 73 through a portion of the movable power assembly PA of the motor, the terminus of the other end extension 74 of the stem normally engages the closed end 75 of a blind axial bore 76 of predetermined depth extending from the inner end of a work-performing element disclosed herein as a plunger 77, with the opposite end of said plunger operably projecting through the circular openings in the end wall lll of the vacuum-motor VM and adapter plate l2 for mounting it to aetuate the master cylinder piston 2t? opposed by spring 25 best demonstrated in FGURE l. The exterior of the inner end or the plunger 77 is provided with a flush circular flange or shoulder 73 to serve as a fulcrum block of larger diameter than shoulder 7l, said shoulders 7l, 78 beinfy coaxially disposed and normally spaced predeterminately to provide an annular variable space 79 therebetween when the stern extension abuts the closed end of the bore 76 best demonstrated in FIGURE 2. Accordingly, the aforesaid piloted connection between the plunger and stem accommodates relative separation of these parts to widen the space normally obtaining between said shoulders for an important purpose to appear.

The improved reaction device generally designated RD comprises a normally relaxed resilient diaphragm or disc SEI?, preferably of circular configuration, and having a central aperture 8l through which the stem flange 71 projects to slidably support the disc in coaxial disposition with respect to the plunger iiange 78, the marginal portion 82 adjacent the perimeter of said aperture being loosely disposed between the shoulders 7l, 78 since the thickness of the disc is, for example, .005 to .007 in. less than the normal Width of tie space between said shoulders to prevent fracture of the disc as a consequence of the hammer-action between the shoulders were the marginal portion of the disc impinged therebetween under tension. The circular marginal portion adjacent the peripheral edge 83 of the disc on the same side as the stem shoulder 7l, is acted on by the pedal 3S via means to be fully described later, to cup (deforrn) the disc forwardly to change it from a substantially iiat plane to a concavity in consequence of the lever-action between the shoulders 7l., 7S with the latter shoulder acting as the fulcrum point which may be varied according to the division of work desired between the operator of the vehicle and the booster unit BM by changing the height of said shoulder 78. This lever-action tends to force the power diaphragm PA rearwardly slightly and to apply pressure on the plunger 77 in a fluid pressurizing direction thus effecting slight relative separation of these two components (see FGURE 6) with the marginal portion 82 encircling said aperture di disposed out of parallel with respect to the shoulders 7l, 78. Accordingly, dishing of the disc as aforesaid induced by the said leveraction sets up a progressively increasing tension in said disc in accordance with the distance the peripheral edge S3 is deected out of parallel plane with respect to the inner marginal portion 82 to thereby serve an initial role of conditioning the master cylinder MC for operation prior to the power phase becoming elfective, and to provide reaction from the master cylinder on the operatoroperated member (pedal) 3L in accordance with the leverage-ratio and tension characterizing the disc for a given diameter, thickness and/or perforation pattern of said disc. This reaction is produced by the vacuum-motor diaphragm PA when energized after the disc Si) has been tensioned as aforesaid, and is transmitted from the shoulder 7l acting on the perimetrical edge of the aperture Si, fulcrum shoulder 78 thence through the disc body to the operator member via the pins 6d carried by the power assembly PA as will appear. As the power diaphragm PA increases its output on the edge of the aperture di, the abnormally separated condition aforesaid of the shoulders 7l, '7d is progressively dissipated until the normal space therebetween is restored wherein the stem extension 74 abuts the end wall 75 of the plunger 77 to provide a straight-through thrust on the plunger 77 from the power diaphragm as is understood, while the peripheral portion of the disc dil is held forwardly under tension by the pedal 35. At the point where the power output is suihcient to reestablish the shoulders 7l, 73 in their normally spaced relation shown in FIGURE 2, whether or not this point defines power-runout, reaction through the disc becomes substantially constant in consequence of the loss of lever-action between the poweractuated shoulder 7l and the fulcrum shoulder 73 on the plunger 77 since the plunger has reached the status of being substantially stationary due to the non-compressible nature of the column of brake fluid as is understood. But, as long as the working force f the vacuum-motor VM is sufficient to effect the braking pressure desired without eliminating the abnormally separated condition of the shoulders 7l, '78 reaction from the master cylinder via the plunger Z7 increases progressively, but not proportionally, as the motor output increases due to the lever-action on and the resilient nature of the disc liti which may also be termed a sprinU-lever since the disc combines lever and spring characteristics for transmission of reaction.

Varying the degree of resiliency in the disc E@ may be obtained in accordance with the springy characteristic thereof and by varying the shape, diameter, thickness or cutouts therein depicted exemplarily in FIGURES 9 through 9E. As demonstrated in these views, the disc Sil may be fabricated with a plurality of inwardly projecting radial fingers (levers) 85 joined at their outer ends by a circular web 36 (FGURE 9A), or outwardly projecting radial fingers 87 joined at their inner ends by a circular web E (FlGURE 9B), or joined intermediate their outer and inner ends by a circular web 89 (FlG- URE. 9C), or their outer and inner ends joined by the circular webs 86, 38 respectively (FIGURE 9D), or a two-finger disc may be employed such las illustrated in FIGURE 9E having opposed sector-shaped cutouts 99 to provide two diametrically disposed inwardly pojecting fingers sil connected at their outer ends by the circular web 86, the inner ends of said lingers being straddle mounted on the stern extension 7d and extending on opposite sides thereof substantially to the axis of said extension for shoulder '7l to act thereon. The resilient characteristic of the disc combined with its lever-action determines the division of reaction force transmitted to the power member PA and the operator-operated assembly P which important feature of the invention will be more fully described hereinafter.

Accordingly, a wide range of reaction discs may be produced by incorporating the illustrated configurations of cutout patterns or combinations thereof in the solid disc shown in FlGURE 9, said cutouts serving to reduce resistance to dishing of the disc. In this manner, the present power-booster apparatus BM may be provided with selective spring-pressure reaction to produce the desired pedal feel according to the type of vehicle and/or pedal system employed, that is, a moderately low-pedal or a normal height pedal which vary in their mechanical advantage according to the distance provided for pedal movement in relation to the full operating stroke of the master cylinder MC.

Slidably mounted on the annular flange 7l of the pilot stem itl is a circular cap-shaped member or spring generally designated 955. 'his spring seat is normally juxtaposed with respect to the forward side of the thrust plate 55 in engagement with the pin heads 65 which move the seat from the thrust plate 55y (see FlGURE 6), said spring seat comprising: a vertical bottom wall 96 constantly engaged by the pin heads 65 and centrally apertured at 97 through which said annular frange 7l projects to slidably support the spring seat in operating position, a peripheral otfset at 98 in the wall 96 provides an inner annular shoulder 99' against which the marginal portion adjacent the peripheral edge 33 of the resilient disc bears, said member 95 terminating forwardly in a circular horizontal wall or flange lill. A normally preloaded compression spring lil?, encircles a portion of the plunger 77 with one end bearing on the inner marginal should-er provided by a counterbore which terminates the opening through the adapter plate l2, such positioning of the end of said spring being accommodated by coaxial openings in the gaskets and end wall lll respectively being of the same diameter 'lll as the counterbore as shown in FIGURE 2. The other end of spring N2. reacts on the opposite side of the peripheral portion aforesaid of the resilient disc Si) to maintain the periphery of the disc dil in engagement with the offset a9' and to urge the spring seat to act through the pins ad on the power assembly PA to move the latter as a unit with the spring seat toward their respective normal positions shown in FlGURES l and 2. `The reaction produced by this spring is in sharp contrast to that produced by the reaction disc St), in that, spring lill offers increasing resistance to the pedal 35 in relation to the distance the edal is moved from its normal position shown in FGURE l and therefore, the reaction transmitted thereby to the pedal is not related to pressure produced by the power assembly PA on the plunger 77. ln fact, the reaction from spring i162 is somewhat transistory serving to provide increasing resistance on the pedal up to the point of the master cylinder MC becoming conditioned to pressurize the fluid therein to effect a braking application under influence of the energized vacuum-motor VM, and thereafter, reaction of the master cylinder becomes substantially constant due to the virtually stationary condition of the parts utilized to pressurize the fluid brought about by the non-compressible column of fluid as is understood. This spring, therefore, serves the novel purpose of supplementing the resilient dise 3l) during conditioning of the master cyiinder MC to pressurize the brake fluid sufhciently to apply the brakes under influence of the vacuummotor VM, but during the fluid pressurizing stage aforesaid, reaction from spring lil?. is substantially constant while the resilient disc 3d continues to transmit a progressively increasing force on the pedal 35 during the powerapplying stage up to the point where the vacuum-motor eects a straight-through operation on the master cylinder MC which point approximates introduction of assistance from the operator as will be more fully explained hereinafter.

T he control valve mechanism generally designated CV is similar in construction and operation to that disclosed in my earlier application Serial No. 684,946 previously referred to and comprises: outer and inner t-elescopicallyrelated elements M5, lll which are disclosed as a cylindrical valve sleeve and valve piston respectively. The valve sleeve JGS is provided with a longitudinal bore tl extending from its inner end to substantially a medial point therein and a reduced coaxial bore li extending from the other end to such depth as to provide a thrust wall in@ between said bores. Spaced from the inner end of the valve sleeve is a vacuum slot liti through the wall thereof communicating with the bore itl? and longitudinftlly spaced rearwardly from said vacuum slot llt) is an air-vacuum control slot lll through the wall of the valve sleeve in diametrically disposed relationship and communicating with the said bore la7, An internal annular groove Trl-i is provided in the surface of the bore lll? afjacent the inner end of the valve sleeve.

The valve piston lee is a spool-type element comprising a pair of longitudinally spaced annular lands llo, 117 which define a ring-like vacuum chamber llti therebetween in continuous communication with the vacuum slot lltl, the outer opposite ends of said lands terminate in reduced diameter cylindrical extensions il?, l2@ respectively. rl`he cylindrical surface of the extension ld is threaded and the free end of the extension il@ is loosely piloted in the opening 63 in plate S6 aforesaid to maintain substantially coaxial relationship between the main control valve mechanism and the movable power assembly PA, and also to enable the end of extension llll9 to engage the confronting surface area on the plate 4S and thereby move as a unit to produce the usual follow-up action requisite for operation of the main control valve means CV provided by the relative movement therein to effect opening and closing of the control-slot lll, The valve land 117 is spaced from the thrust wall $.69 to provide an atmospheric chamber mi therebetween selectively connectible to the dorados lll control-slot lll, said land being termed a working land because it is operable to selectively connect the controlslot lll, to the vacuum valve chamber and to the atmospheric valve chamber lZr, said vacuum valve chamber being subject to vacuum (negative pressure) at all times when the engine is running via the vacuum-slot 1li), such sub-atmospheric conditions being generated, for example, in the engine inlet-manifold (not shown) as a vacuum source. Operably disposed in the valve chamber ft2?. is a normally preloaded compression spring 122 having one end bearing on the thrust wall and the other end pilot-ed on the reduced threaded extension 12h to react on trie confronting face of a preferably hex-type nut 12.3 selectivelv threaded onto said extension to establish the desired prcloaded setting of spring 122, said nut being canable of manual adjustment along the extension away from and toward said land to increase or decrease respectively the tension in spring i222 and thereby vary the degree or" shoe-to-drum contact during the initiatory brakeapplying stroke and reaction on the brake-pedal. This spring is effective to separate the valve piston and sleeve anaccommodate their movement toward each other wile i the limits of the relative operating movement shown rormally obtaining between the inner end of the valve sleeve ltlS and confronting surface area on the thrust late to enable the valve elements to move relatively to each other to control operative energization of the power assembly PA. A split retainer ring 12d engages the groove 11d for engagement by the peripheral outer face portion of the valve land 115 to establish the normal separated status of the main valve elements under influence of the spring as shown in FGURE 2, and wherein the relative operating disposition of the valve sleeve is shown with respect to the thrust plate 5.6 in readiness for a valve operating cycle as will appear.

Encircling the forward portion of the valve sleeve 165' is a valve housing generally designated PH and comprising a pair of interchangeable semicircular segments 128, 12.9 clamped around this portion in airtight sealed relation by a pair of hex cap screws 13d oppositely projecting through holes 131 in a pair of laterally extending ilanges or ears 132 which terminate opposed arcuate portions of said segments, into threaded holes 1?3 through complemental lateral ilanges or ears 134 which terminate the other opposed arcuate portions of said segments to thus tightly clamp the two halves lill, 129 of the valve housing VH on the valve sleeve 165 to provide a unitary assembly thereof. Formed in the inner curved surface of each of the segments 12S, l2@ is a rectangular-shaped arcuate cavity M5, the cavity in the upper segment 123 having continuous communication with the control-slot 111 and the lower Isegment 129 having continuous cornmunication with the vacuum-slot l1@ via the cavity E35 thereof, Aligned wi h the cavity in the upper segment t28 is a rectangular-shaped opstanding embossrnent or boss 136 integral with the circular wall of said segment, and there is a similar' embossinent or boss depending from the circular wall of the lower segment E129. Each of said embossments being provided with a vertical hollow or passageway 132% which communicates with the cavities aforesaid, and a substantially horizontal passageway 139 continuously communicates with each of said hollows. A rigid tubular iitting 11151 is pressed at one end into each of the passageways 139 to provide a vacuum inlet into the interior of the main control valve CV, and an air-vacuum connection from said valve respectively as will appear. The inner ends 142 of the semicircular walls of the segments 12S, 129 in assembled relation terminate flush with the inner end of the valve sleeve 165 to provide a circular working face i143 which continuously engages the ends of the pins ed proiecting through the movable power assembly PA whereby movement of the valve sleeve lds actie ates said pin-s as a unit which in turn simultaneously move the spring seat member disposed adjacent the opposite side of the power assembly PA best demonstrated in lf- Lto URE 2. The aforesaid working face is predeterminately spaced normally from the confronting face area on the plate 56 to establish the relative operating movement of the main control valve means CV whereby movement of the valve sleeve to open `said valve means CV actuates the pins 64 relatively to the diaphragm plates 55, 56 to move the spring seat 95 forwardly away from the plate 55 to additionally compress the sprintT 102 and thereby increasing resistance to movement of the valve sleeve 105, which resistance is progressively induced in accordance with the distance the movable wall PA is moved as a measure of the pressure being exerted by said movable wall on the brake fluid in the hydraulic brake system (not shown). lt should be importantly noted here that during energiZat-ion of the vacuum-motor VM, the spring 102 reacts only on the spring seat 95 and valve sleeve 165 which prevents powehloss that would result should the movable wall PA be required to overcome the force of this spring as is common practice in prior art devices.

lntermediately spaced with respect to the cavities in the aforesaid segments 128, 12% and the rear ends of the circular walls thereof, is a semicircular internal groove 145 which in the assembled status of the housing segments produces an internal annular groove ldd which receives the outer half-diameter in cross section of a split round wire retainer ring 147, and the inner half-diameter thereof engages a circularly aligned external annular groove 143 in the outer cylindrical surface of the valve sleeve 1635 to lock the valve housing segments against relative axial displacement with respect to said sleeve.

Each of the Segments 123, 129 is provided with an indentation or notch l5@ in the rear end of the circular walls thereof and diametrically disposed in their assembled status on the valve sleeve ltlS. rlhese notches register with correspondingly disposed airports lll through the wall of the valve sleeve whereby the atmospheric valve chamber 21 communicates continuously with the power cylinder atmospheric chamber 46.

The power cylinder end wall 3d is provided with a circular opening 154i coaxial with the openinfs in the for ward end wall 11 and associated plates aforesaid, said openinfT 1545 terminates in an outtnrned circular flange 155 which is radially closed inwardly into an external annular groove 156 formed in the outer cylindrical surface of a bearing or support collar 157 to make the collar fast on the end wall 351i. The interior of the collar is provided with an inner counterbore in coaxial disposition with respect to a longitudinal. bore 159 to provide an annular shoulder 16h therebetween, the bore 159 serving as a bearing support for the rearwardly projecting portion of the valve sleeve exterior of the valve housing VH best demonstrated in FlGURE 2. Shoulder 1d@ is engageable by the rear ends of the valve housing segments 128, 129 aforesaid to establish the main control Valve mechanism CV in its normally released position. An other external annular groove lol is provided on the collar l5? rearwardly spaced from the groove 155 for receiving the forward annular enc la?, of a conventional flexible dust boot B.

The free end M5 of the push rod PR projects through a reduced diameter bead 3,66 terminating the opposite end of said boot B into the bore 108 in the valve sleeve 165 to engage the thrust wall lili) whereby movement of the pedal P is transmitted via the push rod PR to initially actuate the valve sleeve 1555 as a unit with the valve piston lilo, followed by relative operating movement of the valve sleeve and piston to control operative energization of the booster motor VM. Upon such relative movement being fully taken up as a consequence of the working face 1.43 engaging the plate 56, a straight-through application of operator input effort is provided against the movable power assembly PA to assist the maximum output effort of the latter to apply the brakes.

A rigid vacuum-inlet tube 17d proiects through the cylindrical wall of casing 41 at 171 (see FIGURE 4), the

aoraioe inner projection portion 72 of said tube receiving one end of substantially a convolution of flexible conduit 173 and the other end of said conduit is attached to the lower tube 141 in the lower valve housing segment i259 whereby vacuum inlet to the arcuate cavity l35 thereof and relative movement of the control valve sleeve 105 with respect to the movable wall PA are provided. One end of another flexible conduit 175 is connected to the free end of an elbow-type tube 176 having its other end secured to and projecting through the plates 55, Se in continuous communication with the power chamber d aforesaid, and, the other end of the last-mentioned conduit being connected to the upper tube Mil whereby the cavity 135 of the upper valve housing segment 1.23 is connected to said power chamber and relative movement between the movable power assembly PA and control valve sleeve 14.05 also provided thereby. The outer projecting portion 177 of the tube ltl receives one end of a third exible conduit SWS and the other end of this latter conduit is connected, for example, to the interior of the engine-inlet manifold (not shown), thereby completing the vacuum line connection to the main control valve mechanism CV.

An air filter device of conventional construction is provided at AF (see FIGURE l) and which is pressfitted or -otherwise secured in an opening it? through the cylindrical wall of the power cylinder casing All for venting the power cylinder chamber d5 to atmosphere via chamber d6, and for ltering out any foreign particles, moisture, etc., from entering said chambers with consequent involvement of the working parts within the booster motor VM. This filter device further serves to silence ingress of air when the vacuum-motor VM is being operated toward released position in response to removing pressure from the pedal P and wherein the motor vehicle brakes are taken olf as is understood.

The reaction plate or disc 80 shown per se in FlGURE 9 is devoid of perforations radially disposed from its central aperture while the modified plates shown in FIG- URES 9A, 9B, 9C, and 9E are so perforated to change the reaction-transmitting characteristics thereof with respect to each other and to the washer-type disc depicted in FIGURE 2, such operating characteristics could also be varied by changing the thickness and/ or adjusting the diameter thereof. Since the plate depicted in FIGURE 9A is typical of the other modiiied plates, a brief description of the construction thereof is deemed apropos as follows: As shown in FIGURE 9A this modified plate is of circular configuration and formed with a plurality of radially disposed perforations or slots as indicated between said inwardly projecting iingers S5, the inner ends of said fingers, define said circular opening 8l. The outer ends of said lingers are interconnected by the web segments 36 to provide the aforesaid circular web tid which engages the offset shoulder 99 on the seat member 95 aforesaid. rIhe inner marginal portions 32 of the fingers are operably disposed between the plunger shoulder 7S and pilot stem shoulder '71. These fingers may be interconnected at their inner ends by web segments as indicated to provide the aforesaid circular web S3 disposed between the shoulders 7l, 78 as demonstrated in FEGURBS 9B, 9D, or interconnected intermediate thereof by web segments depicted in FIGURE 9C to provide the aforesaid circular web 89, or the sector cutouts 917 as shown in FEGURE 9E may be employed to provide the aforesaid circular web S6 with two diametrically opposed lingers 9i aforesaid. Accordingly, the disc titl may be provided with numerous perforated patterns to change the resilient characteristic thereof for a given thickness of material and diameter, and further the leveraction ratio may be modified by adjustinfT the relative contact points on the shoulders 7l, 78 and seat member 95 to modify the reaction force effective on thecontrol valve sleeve 165 and therefore the pedal 35 whereby the force exerted on the pedal may be adjusted to suit the particular installation and/or operator preference.

The auxiliary or vacuum relief control valve AV comprises a longitudinal circular passageway 1% radially offset from the axis of the main control valve CV, and which extends through the plates 55, 5S, 56 in that order to normally place the power cylinder chambers d5, lo in communication with each other when open, thereby balancing pressures on opposite sides of the movable power member PA.' The end of this passageway on the plate 536 terminates in an annular preferably tapered valve seat 195. A poppet-type valve element i927 is movably disposed in the passageway and provided with a head 198 having a complentental face :for engaging the said valve seat to close said passageway. Projecting from the head through the passageway is a stem Ztial having a plurality of elongated radially disposed fins 265i of substantially the same overall diameter as the passageway, to slidably guide the valve element into engagement with its valve seat aforesaid, said iins providing longitudinal spaces Ztl?.- therebetween to enable air flow through the passageway when open. The stem operably engages a confronting portion of the back of the spring seat member 9S in normal disposition as shown in FG- URE 2 to move the head of the valve element 1&7 away from its cooperating seat and thus connect the chambers d5, @lo so that pressures on opposite sides of the movable power member PA are balanced. The length of the stern in@ is such that upon movement of the spring seat member away from the thrust plate S5, under influence of the pedal l), that the poppet valve engages the seat 196 to isolate the chambers 12,5, 46 from each other thereby conditioning the movable power member PA to be subject to differential pressures on opposite sides thereof induced by opening the main control valve CV after the poppet-valve F197 has been seated. lt should be noted in this connection that the valve sleeve los and spring seat member g5 move as a unit and the timing of the opening of the control-slot lll to evacuate the power chamber l5 of air is such that this latter operation transpires as or after `the poppet-valve closes in the manner explained above, otherwise, air in the power chamber da could not be evacuated to create such differential pressures under control of the main control valve CV since chamber would be connected to atmosphere via chamber d5. Stated differently, the poppet-valve must be closed before the main control valve CV can be effective, even though open, to energize the vacuum-motor VM. This poppet-valve may be termed a vacuum-relief or auxiliary air valve since its function is to place both chambers of the power cylinder VM in communication with atmosphere in cooperation with or independently of the main control valve CV, upon removal of foot pressure from the pedal P at any applied position thereof, to enable the return springs aforesaid and pressurtd on the brake fluid to effect quick return of the mechanism to brake off position irrespective of the rate of withdrawal of the foot from the pedal whereby the operating parts associated with the pedal keep pace with it toward their fully released positions. in this way, a slowe brake release is prevented thus making it possible to apply and release the brakes as rapidly as conditions require. Of course, the control-slot lll could be made wider and deeper in the valve sleeve ltl with the valve working land Ill? proportionately widened to accommodate a more rapid ingress of air into the power chamber 5S when taking the brakes olf but such would act adversely to a smooth sensitized control of the booster motor VM in relation to the shortest possible pedal travel requirement to effect operation of the main control valve CV to energize the motor VM. Accordingly, the poppetvalve preferably serves as an auxiliary air inlet to the power chamber de" in cooperation with the off position of the main control valve CV so that release of the vehicle brakes occurs in synchronism with the rate of relll moval of foot pressure from the pedal P; but if the main control valve CV is slowly released, ingress of air via the control-slot 1li into the power chamber i5 enables the retraction of the operating parts simultaneously with pressure removed from the pedal as is understood. En either case, however, venting of both motor chambers d5, 45 to atmosphere by the poppet-valve at full release of the pedal pressure assures that the operating parts are fully established in their respective released positions wherein the master cylinder compensating port is fully uncovered for the fluid to properly adjust in the hydraulic system. Partial evacuation of the power chamber l5 tends to draw the poppet-valve head i538 toward its seat by the air pressure effective on the opposite side of the cad and thus seal off the chamber i5 from the chamber 415, however, a normally pretensioned ilat spring is provided with one end anchored as by a drive pin 2d@ on the plate 56 and the other end overlying the valve head to react thereagainst to insure seating or" the head when the stem 25d is released by movement of the spring seat member 95 away from the thrust plate 55 as shown in FEGURE 6 where slight clearance obtains between the end of the stem and vertical wall of the spring seat member Closed condition of the relief valve must coincide with the lapped position of the working land 117 and control-slot 1li to enable holding the brakes Non.

The support collar 157 is further provided with radial passageway 2d? which is ilared at its outer end, and the inner end of which intersects an internal annular channel 29d formed the bore rQ. An oil saturated ring-type wiel; 2d? is carried in this channel in encircling relation with respect to the exposed exterior cylindrical surface of the valve sleeve ldS, to provide lubrication or this surface and the surface or the bore 159. A ilat having a shoulder- 2l?. is provided in the outer surface of the valve sleeve 1655' which communicates with the wick 2; in the normally released disposition of the control valve mechanism CV shown in FIGURE 2, said flat having continuous communication with the upper air port whereby ingress of air through this port induces the lubricant suspended in the wick to move toward said air port and thence into the interior ci the sleeve to lubricate the valve piston The 'aforesaid shoulder which terminates the rear end o the liet 21d tends to wipe the lubricant from the wien during sliding movement of the sleeve INES relative to the collar lS which wiping action cooperates with the air llc-w into the interior of the valve sleeve 195 to place at intervals small quantities of lubricant near the port 151 so that it may be drawn into the interior of the sleeve. In this manner an efficient lubricating system is provided for the working parts aforesaid by simply introducing periodically a small quantity of oil as by the spout of an oil can engaging the flared end of the passageway 2W, to maintain the wick saturated. Overlubrication is prevented by the control-slot 111 and bottom air port 51 which drain oil excess oil, the port 151 con- 'veyinor such excess to the atmospheric chamber i6 of the vacuum-motor VM, and any excess oil reaching the cavity in the lower valve housing via control-slot lil when the main control valve CV is disposed as shown in FEGURE 2, would be drawn into the valve vacuum chamber 113 when the motor is energized with consequent lubrication of both of the valve lands, and any exc-css lubricant in the valve chamber would ultimately reach the engine inlet-manifold (not shown) under influence of vacuum and be dissipated in the combustion chambers of the engine as is understood.

peraz'on The operation of my improved booster brake mechanrsm BM will be apparent from the foregoing description but may be summarized as follows:

Assuming the device BM is installed on a motor Vehicle as the present disclosure exemplarily demonstrates in FlGURE l, to operate the hydraulic brake system (not shown) commonly employed on such vehicles, is in released brake oli condition as depicted in FIGURES 1 and 2. With the engine running, sub-atmospheric pressure (vacuum) is produced within the inlet-manifold (not shown) which is conveyed through conduit 178, tube 170, conduit 173, tube 141, cavity 135 in valve segment 129, and vacuum-slot 11d to evacuate the air from annular space 118 on the valve piston 106 which conditions the main control valve mechanism CV for operation to control operative energization of the Vacuum-motor VM.

1n the norma'ly released disposition of the valve sleeve and piston lllS, 1% portrayed in FIGURES 1 and 2, the vacuum power and atmospheric chambers 45, 4d respectively are vented to atmosphere, the power chamber 45 being rented via the elbow-tube 176, conduit 175, tube 141, cavity 135 in valve segment 128, passageway 139, control- Slot 111, atmospheric valve chamber 121, ports 151, notches 15d, atmospheric chamber 46 and the air filter AF, and, as previously stated, the chamber 45 is in continuous communication with the atmosphere via said ilter device. Also the vacuum relief valve AV is in open disposition as shown in FIGURES l, 2 and 7 thereby cooperating with the control-slot 111 in the main control valve CV in normally released position to unrestrictedly accommodate free llow of air between the motor chambers d5, i6 to balance the pressure therein. Accordingly, the power cylinder VM and related parts incuding the power assembly PA are in their respective normally released positions as shown in FIGURE l in readiness for a brake-applying cycle.

Initial depression of the pedal 35 to the first dashed line position in FIGURE l moves the valve sleeve and piston 105, HB6, power member PA and duid-displacing unit comprising the hydraulic piston and related parts as a unit, which unitary operation simultaneously adr varices the cup seal 31 against the action of spring 25 to the position of FIGURE 6 wherein the compensating port 27 is closed thereby conditioning the master cylinder MC for operation to apply pressure on the liquid in the pressure chamber 24 and displace it through the one-way checl valve 22 into discharge port 23 and thence via the hydraulic lines (not shown) into the wheel cylinders (not shown) to expand the brake shoes (not shown) into contact with the internal frictional surface on the brake drums (not shown) rotatable with the vehicle wheels (not shown) to apply the brakes as is understood. This unitary initial movement of the parts aforesaid is effected by operator force on the pedal 35 acting through the preloaded thrust-transmitting capacity of the main control valve return spring 122 and resistance of the reaction device RD aganst deformation (dshing) to place it under tension. Valve spring 122 is preferably installed under l5 to 20 pounds, or may be lighter where the reslent plate is designed to produce sullicient tension to effect the aforesaid unitary movement of the parts as a preliminary conditioning operation to the master cylinder MC prior to operating to pressurize the fluid therein sufficiently to lirmly set the brakes. In any case, however, spring 122 must be installed under suiicient tension to overcome the reaction from spring 25 otherwise the aforesaid initial movement ofthe parts as a unit cannot be accomplished under influence of the pedal 35 operated from its normally released position wherein the vehicle brakes are "off, and also the main control valve CV is in closed olf position and the auxiliary valve AV open. Spring 25 in convenional practice is usually set to establish a normal preloaded condition of around 5 to 10 p.s.i. against the resdual pressure valve RV to establish a minimum line pressure within that range external to the pressure-working chamber 24.

As the power member PA and fluid-displacing unit initially move leftward as a unit to close the compensating port 27 under influence of initial operator eort on 17 the pedal 35 transmitted through the preloaded valve spring 122 supplemented by resistance from the disc Sii to cup as defined by the first dashed line position of the pedal in FIGURE l, increasing pressure on the pedal, pressurizes the uid in the master cylinder MC at substantially the same pressure as the preloaded tension of said valve spring; whereupon, more pressure on the pedal acts to irst cause the spring 122 to yield and the resilient disc 80 to dish into a somewhat cupped configuration as shown in FIGURE 6 to place the disc under tension. This yielding ofthe spring 122 and simultaneous capping or dishing of the disc 80 enable the valve sleeve 105 to move relatively to the valve piston 106 thereby disposing the control-slot 111 with respect to the valve working land 117 to isolate the atmosphereic valve charnber 121 from said slot and to connect the vacuum valve chamber 118 thereto and thereby connect the source of vacuum to the power chamber 45 via the conduit 175 to evacuate the air from said chamber causing differential pressures to be effective across opposite sides of the diaphragm plates 40, 41 to thus energize the vacuum-motor VM. During the tensioning of the reaction disc 80 in the manner above stated, the lever-action thereof tends to separate the work-performing element 77 from the shoulder 71 carried on the pilot stem 70 rigid with the diaphragm thrust plate 55 (see FIGURE 6), and thereby widen the space 79 to condition the reaction disc to transmit reaction from the master cylinder IVIC to the brake pedal. This lever-action induces a slight rearward movement to the valve piston 106 relative to the forward move- Q ment of the valve sleeve 105 under influence of the pedal 35 to bring about the open on position of the control valve CV, such relative movement of the control valve members 105. 106 and separation of the plunger 77 and thrust plate 55 resulting from the substantially stationary condition of the fluid-displacing unit (hydraulic piston 20) effected by the non-compressible column of brake fluid between the head of the piston 20 and wheel cylinder pistons (not shown) as is understood. The aforesaid relative movement of the control valve sleeve 105 moves the control-slot 111 into increasing exposure with respect to the annular vacuum chamber 118 after the valve piston working land 117 laps said control-slot to cutoff communication thereof with the atmospheric valve chamber 121, thus enabling evacuation of air from the power chamber 45 via the elbow-tube 176, conduit 175 and connected arcuate cavity 135 in the upper half 128 of the valve housing VH, control-slot 111 and vacuum chamber 118. As air is evacuated from the power chamber 45 differential pressures are set up on opposite sides of the power member PA causing it to move further leftward from the position shown in FIGURE 6 to actuate the hydraulic piston 20 to provide power assistance in applying the brakes. Prior to the vacuum-motor VM becoming energized as aforesaid, the resilient disc 80 is deformed into a cupped configuration from its normal flat relaxed status. This deformation of the disc 80 is effected by operator force on the control valve sleeve 105 acting through the pins 64 against the movable seat member 95 to set up tension in said disc, and simultaneously with this tensioning action on the disc, the marginal portion of the disc adjacent the edge of the aperture 81 additionally separates shoulders 71, 78 by lever-action therebetween which correspondingly widens the space 79 normally obtaining between said shoulders. Duringthis lever-action imparted by the disc, the power member PA and valve piston 106 move slightly rearward as a unit against spring 122 relatively to the valve sleeve 105 due to substantially stationary condition of the plunger 77 induced by the non-compressible column of brake fluid whereby the shoulder on the plunger serves as a fulcrum to produce such lever-action through the disc 80 between its pressure points at the periphery thereof against the offset shoulder 99 on the movable seat member 95 and the circular edge of the aperture 81 against the shoulder 71 carried by the thrust plate 55. Accordingly, spring 122 plus resistance of the d-isc S0 to dishing force the fluid displacing unit leftward to operate the master cylinder MC to take up the slack in the hydraulic lines until a point is reached whereat pressure en the brake fluid and reaction from spring 25 reach a factor substantially equal to the preloaded status of valve return spring 122 and resistance to dishing provided by the disc which cooperates with the spring 122 to additionally pressurize the brake fluid as the vacuum-motor VM becomes energized.

At the point of relative movement between the control valve sleeve and piston where the control-slot 111 is cracked placing the vacuum source in communication with the power chamber 45, the inner marginal portion of the reaction disc is disposed at an angle with respect to the confronting abnormally spaced faces on the shoulders 71, 78, and the peripheral marginal portion of the disc is disposed out of plane with said shoulders. Thus, it may be said that the reaction disc 80 is now conditioned to transmit reaction from the master cylinder MC to the pedal mechanism P. As the output effort of the motor VM increases it is transmitted progressively through the resilient lever-action of the disc to the peripheral marginal portion of said disc with said plunger shoulder 75 acting as the fulcrum. This progressive reaction transferal from the master cylinder continues until the shoulders 71, 78 are forced into normally spaced relation wherein the full inner marginal portion of the disc therebetween assumes substantially parallel relation with respect to said shoulders and the stern extension 741 abuts the closed end 75 of the plunger bore 76. At this stage of power output, it may be said that a state of powerrun-out has been reached, that is, the motor VM is providing maximum output which if insufficient to bring about the braking force required, the operator may increase his effort on the pedal 35 to make up such deficiency whereby the working end 143 of the valve sleeve 105 and housing VH is brought into engagement with the thrust plate 56 to enable a straight-through application of joint effort from the motor and operator on the hydraulic piston Z0. With this arrangement, the operator can instantly and automatically cooperate with the maximum output from the motor VM to apply the brakes directly at any time. Thus, the operator may team up with the motor VM at any time automatically by merely pressing through on the pedal mechanism P to bring about maximum stopping effort, and particularly stops in the einer* gency-panic category which the motor alone is not powered to handle. When the straight-throng operation aforesaid is made effective, the end of the extension 74 on the pilot stem 70 is disposed in engagement with the closed end 75 of the axial bore 76 which slidably receives said extension to support the confronting end of the work element 77, and the reaction disc 80 is deformed into its maximum cupped condition which becomes slightly forwardly of the position shown in FIGURE 6, whereby reaction from the master cylinder is transmitted by the disc at substantially a constant factor to the brakeedal with the space 79 restored to normal width as shown in FIGURES 1 and 2. Accordingly, operator force is transmitted through the push-rod lPR directly to the outer valve element 165, but at this point such force is transmitted indirectly along two paths; namely, (l) via the valve spring 122, power assembly PA, pilot stem 70, work element 77 and connected piston 20 in opposition to reactive spring 102 and piston return spring 25, to move these parts as a unit to effect slack take-up, and (2) via pins 64 to slidably actuate spring seat 95 relatively to the power assembly PA in opposition to reaction from spring 102 and resistance of the reaction disc 80 to cupping, to effect relative displacement of the valve elements 105, 106 to open position as shown in FIGURE 6 upon the piston 20 and work element 77 reaching a substantially stationary position against the non-compressible column of brake fluid, and said operator forces are aora,

directed along ya third path to effect said straight-through operation by bringing the inner end of the outer Valve element 165 into engagement with the power assembly PA, and thence via the engaged condition of the pilot stem 76 with the work element 7'7 to the connected master cylinder piston Ztl. While the resilient nature or" the reaction disc Sil eliminates propo-rtional application of effort by the operator and motor VM, it does serve to provide a simple and eicient mechanism for transmitting the necessary increasing reaction to the pedal mechanism P to enable smooth energization of the vacuum-motor. It should be importantly noted that this novel disc reaction principle is a continuous force-transmitting means, that is to say, the disc does not divert and/or absorb any of the motor and operator operating forces, but to the contrary, all of such forces are transmitted undiminished to actuate the hydraulic piston 2d to effect operation of the vehicle brakes.

It is thus seen from the foregoing description of the operation of the resilient disc Sii, that actually the slack take-up and initial pressurizing of the brake fluid defined by the dashed line positions respectively of the pedal mechanism P in FIGURE 1, are effected in two stages; namely, the rst stage is effected through the force transmitting capacity of the preloaded status of the valve return spring 122 and resistance to dishing by the disc Sti, and the second stage effects increased pressure on the brake fluid to a point of substantially halting movement of the fluid-displacing unit (hydraulic piston Ztl) in response to the amount of operative force required to overcome the normal status of both the disc 80 and spring7 122 prior to the vacuum-motor VM becoming energized in the manner above stated. Stated differently, the force applied to initially operate the pedal mechanism P to its first dashed line position shown in FIGURE 1 and corresponding to the operated status of the booster mechanism BM shown in FEGURE 6 is impressed on the plunger 77 via the yielding disc 105 and spring 122 aforesaid up to the point at which movement of the plunger and piston is arrested, whereupon further pressure on the pedal receives reaction from the master cylinder MC as a factor of the tension and lever-action of the disc and spring 102 until the power output is at a maximum whereat the reaction from the master cylinder becomes substantially constant on the pedal mechanism since the latter has now joined the power member PA to effect maximum pressure on the brake fluid should such be required.

The utilization of combined tensioning and lever-action characteristics of the disc 8i) produce an extraordinary advance in the art to apprise the operator with a measure of the braking pressure effective at a given position of the pedal mechanism P, and while this reactive force from the pressurizedstatus of the brake fluid is not impressed proportionally on the powerand operator-operated members PA and P respectively, it does serve in a new and improved manner to enabe smooth mergence of pedaland power-actuated forces under operator control and thus, the novel reaction device aforesaid provides the operatorwith a measure of the braking force in effect simulating the more expensive and complicated types of power-brakes which utilize a coaxial hydraulic piston or reaction lever system which transmits hydraulic reaction only upon motor operation, to provide a proportional measure of the total effective pressure on the brake fluid generated in conjunction with a larger hydraulic piston actuated by power means, and too, sealing problems are eliminated since the present vacuum-motor VM accommodates the conventional master cylinder such as illus` trated in FGURE l.

Spring 102 serves to stabilize the disc 30 on the spring seat member 95 and is characterized by increasing tension on said member above a normally preloaded status progressively induced in response to the distance the pedal mechanism P is moved from released position in a brake-applying direction before the plunger 77 is halted in the manner aforesaid, at which point the reaction from this spring becomes substantially constant on the pedal mechanism to supplement the reaction forces transmitted by the disc Sti. The booster apparatus BM is completely operative without spring 102 since spring 25 alone has the capability of returning the fluid-displacing and motor parts to their respective released positions, however, if added resistance to pedal movement during the slack take-up stage is desirable for better braking control, spring 162 would be highly satisfactory for this purpose, and too, it would serve the additional function of reacting on the power member PA via the spring seat member in engagement with the actuatable pin heads 65 to assist in returning the power member to its normally released posit'cn shown in FIGURE l, but when the seat member is disengaged from the power member by the pedal 35 as shown in FIGURE 6, the force of this spring is removed from the power member so that the vacuumrnotor VM does not operate against it in a brake-applying direction. Spring 102 possesses another useful function as a supplement to spring 25 to provide a more rapid and sensitized return action on the fluid-displacing and motor parts, and therefore a quicker release of the brakes than would be provided by the spring 25 alone since this latter spring is penalized by a maximum preloaded status and operating rate to control the residual pressure valve RV. Stated differently, spring 25 cannot be rated higher than the requirements for control of the residual valve, and therefore, if reaction from this spring is insufficient to rapidly return the operating parts of the booster apparatus BM to their respective released positions as shown in FIGURE l after a brake-applying operation thereof, then the only recourse is to add the spring 102 to obtain the added force to effect such quick release of the parts and at the same time augment resistance to initial slack takeup to condition the motor VM to operate.

Further considering the operational behavior of spring 1%, it should be noted that it produces control characteristics in the way of reaction aganst which the valve sleeve 105 is adjusted to control operative energization of the vacuum-motor VM. This reaction increases above normally preloaded status of this spring in direct proportion to the distance the brake-pedal 35 is depressed, and therefore, such spring resistance alone would not ne-es sarily have a magnitude correlated with the amount of braking force in effect at every position of the brakepedal, and too, pedal-load would increase toward the end of the full operating stroke of the plunger 77 actuated by vacuum-motor VM to an undesirable degree which would defeat the objective of reducedI pedal effort.

As spring im is additionally compressed above its normal preloaded status, it provides increasing resistance in relation to pedal movement up to the point where the fluid becomes pressurized, and thereafter, resistance becomes substantially constant on the brake-pedal 35 as a consequence of the substantially stationary condition of the fluid-displacing parts acting on the non-compressible column of fluid as is understood. Since the fluid becomes pressurized at different stations along the full operating stroke of the motor-actuated plunger 77 due to wear on the brake linings and parts, and to minor leakage of the various seals in the hydraulic brake system, it will be appreciated that if the pressurized state of the fluid to apply the brakes becomes effective toward the end of the full operating stroke of the plunger 77, that reaction from the spring 162; can become severe resulting in a moderately hard-pedal due to rapid build-up in the force of this spring from its normally preloaded status, the latter providing the operator with accurate sensing in initially applying the brakes thus preventing sudden braking applications which could possibly result in a power-surge if the operator lacks this awareness as he initially applies the brakes.

Reduction of this spring principle to commercial 2l usage, demonstrated that the preloaded weight should be approximately Ztltt and rated at maximum compression corresponding to the end ot the full operating stroke of the work-performing element 77 at 6G# pressure which when transmitted through the pedal leverage ratio reacts on the operators foot at 5 to l5# through the full operating range of the plunger '77 where a normal height pedal is employed; but if the pedal ratio is lowered to accommodate use of a low-pedal with less mechanical advantage, reaction from this spring increases proportionally to a limited extent that converts the low-pedal into a moderately hard-pedal as aforesaid through the stage of operating the valve sleeve 195 and piston ldd from normal positions to operating positions to control operation of the vacuum-motor VM. Accordingly, this spring serves to best advantage as a reaction means by utilizing its yielding resistance through substantially the first-halt of the series of pressurizing movements along the full operating stroke of the plunger 77 which may be had by keeping the brakes prop-erly adjusted and the system free of leaks which service operations contribute to safer driving. lf a lower rated spring is utilized then reaction of sufficient magnitude at points beyond the haltdnark of the plunger stroke in a pressure applying direction would not provide the operator with the necessary physical perception of the braking force applied.

The foregoing operation completes what may be termed the applied stage. With the brakes in applied condition, if operator effort on the pedal 35 is halted, the power member PA will slightly advance relatively in a brake-applying direction carrying with it the valve piston lilo relatively to the control valve sleeve ltlS to produce what is termed the poised or holding stage at substantially any applied position of the hydraulic piston Ztl. This latter operating stage results from the usual followup action of the control valve elements ltlS, lilo by a lapped (closed) condition ot control-slot lll with respect to valve working land ll' induced by the aforesaid slight relative movement of the power assembly PA with respect to the valve sleeve 195 in the event brake pedal movement is halted as exemplified in FIGURE 6 by the dashed line position ol valve land M7. Thus, the brakes may be held on with minimum operator effort on the pedal 35 as a result of substantial countern balance between the differential pressures acting ou the power diaphragm PA and the existent hydraulic pressure in 'the hydraulic lines against the head of the piston Zd. if the motor VM should fail to be effective to provide power assistance, the force exerted by the operator on the pedal 35 will bring the inner end 1453 of the control valve housing VH and sleeve ltlS into engagement with the confronting plate 5d, and wherein the relative movement aforesaid therebetween is fully taken up and the pair or" valve elements ltlS, lilo relatively positioned wide open or on with respect to the vacuum source and power chamber d5", enabling the operator to operate the hydraulic piston Ztl directly by physical force alone if necessary to attain displacement of liquid in the hydraulic lines according to the braking force required to stop the vehicle. With the power phase effective, however, incremental depressing and releasing movements of the brake pedal induce corresponding follow-up movements substantially of the power assembly PA to apply and release the vehicle brakes in a manner replete in the power brake art.

Due to the exactness of the followup action of the control valve means CV and the ever present reaction of the springs lil-2, m2 on the pedal 35, there is never any tendency of the power phase to over brake at any given applied position of pedal movement which contributes the highly desirable feature of smooth stops at low vehicular speeds with instinctively predictable control. At high speeds dangerous grabbing or locking of the vehicle ground wheels is prevented thus producing smooth vehicular deceleration with reduced operator efort, in accordance with the pressure applied on the brake pedal.

Since the auxiliary air valve AV cooperates with the oft (air incursion) position of the main control valve CV to establish equivalent pressures on opposite sides or the power assembly PA for power-inactivation of the booster motor VM, it is obvious from the disclosure that such oit position of the main control valve may be eliminated by widening the working land lll? sufficiently to overlie the control-slot lll when the control valve elements are in normal oil disposition as shown in FIGURES l and 2, and thereby dispense with the function of the atmospheric valve chamber lil., so that the incursion of air into the power chamber 45? is controlled solely by the auxiliary air valve AV in such manner that the vacuum-control of the main control valve CV is synchronized therewith to produce what may be termed the control valve means for the power assembly PA, while excursion of air from said chamber to produce differential pressures on opposite sides of the power assembly is under sole control of the main control valve. ln this obvious modilication of the control valve assembly, additional auxiliary air valves or enlarged capacity of the one auxiliary air valve shown would have to be provided for rapid incursion of air into the power chamber l5 to sensitize brake release.

The hydraulic pressure chamber 2dbeing conventional in construction and operation, enables the operator to pump the brakes to prevent dangerous brake fade whether the power phase is effective or not. Thus on long downgrade operation of the brakes may be carried out in cooperation with power assistance or .independently thereof in the usual manner by pumping the pedal to introduce more liquid from the reservoir 26 via the intake port 2S, ports 29, cup seal 3l into the pressure working chamber 2d. During brake-applying movements of the hydraulic piston 2li the pressure developed thereby on the cup seal 3l firmly seats the peripheral outer side of the back wall thereof on the face of the head to thus close the forward ends of the ports 2% preventing escape of the liquid under pressure from the chamber 24- back to the reservoir 26.

When pressure on the pedal 3d is removed, springs 25, 102, M2, and the diaphragm reactor @il react to reset the fluid-displacing unit, power-diaphragm and control valve CV into their respective released positions shown in FIG- URE l, the spring seat member 9i being biased into engagement with the forward side of the thrust plate S5 via pin heads 65 by spring lll?. to assist in the :return of said assembly and control valve elements to their respective released positions wherein the relative movement between the power diaphragm and control valve sleeve 05 is re-established through cooperative influence or the springs ltlZ and M2 which spring operations assist in reestablishing the released or brake od position shown in FGURE l in which the power chamber 45 is again in communication with atmosphere via the open relief valve 197 and control-slot lll vented to air via valve air chamber 121i and ports ll. As air enters the power chamber d5 via control-slot lll, chamber tl, ports l'l, and conduit ld, the differential pressures are reduced, and eventually dissipated, enabling springs 25 and ltlZ to return the hydraulic piston 2u and plunger 77, and power diaphragm PA to their respective released positions portrayed in FIGURE l wherein the rear end of the control valve housing abuts the collar shoulder 160.

During the return stroke, a predetermined pressure is retained in the hydraulic lines by means of the conventional residual pressure check-valve RV as is understood. If the pressure in chamber 24 falls below atmospheric pressure during the return stroke, brake fluid is drawn through ports 29 from the reservoir 26 past the cup seal 3l into the chamber 24 to maintain said chamber filled. When the brakes are fully off or released as shown in FIGURES l and 2, the residual check-valve RV inlluenced to seat by spring 25 will establish the minimum residual pressure 'in the hydraulic lines, such as, for example, 5 to l p.s.i., and with the port 27 uncovered excess liquid in the system returns through said port to the reservoir and vice versa if additional liquid is required in the system. Therefore, the port 27 is termed a compensating port.

If the power phase is disabled or inadequate for any reason, pressure applied on the pedal mechanism P actuates the hydraulic piston Ztl straight-through in the well known manner with increased operator eii'ort, however, being required as is understood where the factoryinstalled pedal mechanism is the sole actuating medium for the brakes. Thus, my improved booster-operating mechanism BM may be operated in usual pedal fashion with no additional force required over that normally employed in operating the conventional hydraulic brake system devoid of power assistance.

My improved booster device BM is designed primarily for use in brake installations, such as found on motor vehicles, which are operated preferably by a suspendedtype pedal rather than the conventional brake pedal extending through the toe board of the floor in the drivers compartment. Use of the pendant-type pedal as the brake control member simplifies control of the oral-ies since the device BM can be readily installed in the engine compartment on the firewall for accessibility and at the same time enables movement of the pedal foot pad which the operators foot engages in accordance with the stroke desired. That is to say, if a lower pedal is desired, length of the push rod PR is adjusted accordingly to establish the pedal pad closer to the toe board, while if a higher pedal is desired the push rod PR would be lengthened to place the pedal pad normally farther away from the toe board. Lowering of the pedal is limited since such travel must be proportionate to the full operating stroke of the hydraulic piston 2li. The low-pedal pad adjustment aforesaid removes some of the time lag incident to the operator transferring his foot from the accelerator to the brake pedal and vice versa, and therefore, under certain driving conditions safety in control of the vehicle may be somewhat enhanced. However, actual driving oxperience with a car equipped with my novel booster mechanism BM, dictates that the longer pedal travel is conducive to better power-braking control through the full vehicular speed range, and added safety is provided should the power phase be inadequate or fail by having the longer operating stroke instantly available to operate the master cylinder MC in the usual pedal fashion without interference from the disabled power cylinder VM. Furthermore, it is difficult to provide feel control in a brake operating device of the type under consideration without a degree of pedal movement, rather than a sensitive touch pedal travel which tends to cause sudden and erratic operations of the power device VM, because the operator is deprived of a definite resisted movement of the pedal control prior to the power becoming effective. It is this latter serious disadvantage common in prior art devices that my improved brake operating device basically seeks to overcome by providing suflicient brake-applying movement of the pedal mechanism P prior to bringing in the power phase so that lurching stops are avoided, the operator being able to blend the pedal action in taking up substantially all of the slack in the system, with the power phase to produce smooth brake applications under all driving conditions of the vehicle irrespective of the mode of pedal manipulation.

Further considering the relative preloaded strengths of the springs 2S, E22, it has been found in commercial practice that the weight of spring lZZ should, preferably, be greater than spring 25 and therefore capable of overcoming this latter spring to bring about the conditioning of the hydraulic master cylinder MC for operation in the manner previously described. However, springs i221, 25 may be designed to substantially counter-balance each other in their respective preloaded status and still provide smooth mergence of the power phase with the initial footoperated phase, but, with the weight of spring lZZ greater than the preloaded weight of spring 25, spring l22 is capable of not only overcoming spring 225 but also of transmitting initial movement to the hydraulic piston Ztl sufiiciently to close the compensating port 27 and subsequently develop some pressure on the brake fluid in the hydraulic lines to provide the operator with a feel ci resistance to pedal movement as a signal that inauguration of the power phase is imminent so that unusual smoothness with reduced physical eort results. Where spring 122 is appreciably less or substantially equal to the preloaded status of spring 25, operation of the present booster mechanism BM becomes somewhat erratic and less controllable due to the power phase being inaugurated concurrently with or before the foot-operated phase rather than in the former preferred sequence of following the foot-operated phase. ln the arrangement where the power phase leads the foot-operated phase, spring T122 would be insutliciently preloaded to give the driver any appreciable degree of resistance to pedal movement and, therefore, the power phase would be brought in with less control on the part of the driver, and too, the power cylinder VM would become energized suddenly and move initially rapidly since the liquid in the pressure chamber 2licannot be pressurized until the compensating port 27 is closed which lwould virtually give the hydraulic piston 20 free unresisted movement through its initial phase before the pressure chamber 2li becomes conditioned by the power device VM rather than in the preferred more controllable arrangement by initial pedal stroke. As will be appreciated, such idle free movement of the power diaphragm PA and associated duid-displacing parts accelerates initial operation of the power cylinder VM and consequently effects a sudden build-up of the pressure inthe hydraulic lines tending to over-brake, and at low speeds of the vehicle, produces a locking effect on the vehicle wheels to the discomfort of the passengers and added danger of a collision from a vehicle following to the rear.

From the foregoing discussion of the relative strengths of the springs E22, 25, it is contemplated that these two springs should, preferably, be tensioned in their respective preloaded status with spring 122 stronger than spring 2S, and that the reactive and return spring 162 should preferably be installed with such tension as would provide the operator with a degree of initial pedal resistance to signal inauguration of the power phase for smooth braking control for all stopping conditions with less expenditure of physical effort throughout the full operating stroke of the pedal mechanism P. It is irnportant to note that the resilient disc Sil also plays an important role in the pedal feel produced by my improved vacuum-booster BM since this disc resists deflection during the conditioning of the master cylinder MC for operation thus assisting in its conditioning phase, and subsequently transmitting reactive forces from the master cylinder progressively as the vacuum motor output builds up to give the operator a definite sensing of the relation of his input to the output effort of the motor to the point of power run-out.

The interaction of the control valve CV, power diaphragm PA and the reaction disc Si) produces a novel and patentable arrangement, and features of construction and operation of the cooperating elements of these components and more efficient cooperation of such elements during the opening phase of the control valve CV as depicted in FIGURE 6, to dish the disc into a conguration similar to a Belleville washer. The outer peripheral portion 83 of the disc is moved forwardly relatively with respect to the inner marginal portions of its ngers which tends to widen the space 79 normally obtaining between the shoulders 7l, 7S. This spring-lever action is induced by the substantially stationary condition of the plunger 

1. A FLUID PRESSURE ACTUATED MOTOR COMPRISING: A CASING AND A PRESSURE-RESPONSIVE UNIT MOVABLE THEREIN FROM A NORMALLY RELEASE POSITION; AN OPERATOR-OPERATED MEMBER HAVING A NORMALLY RELEASED POSITION; A MOVABLE MEMBER MOUNTED ON SAID PRESSURE-RESPONSIVE UNIT COAXIALLY THEREWITH; FOLLOW-UP CONTROL VALVE MECHANISM HAVING A MOVABLE PORTION MOUNTED ON THE MOTOR CASING, AND ANOTHER PORTION OPERATIVELY ASSOCIATED WITH THE PRESSURE-RESPONSIVE UNIT TO MOVE AS A UNIT THEREWITH, SAID VALVE MECHANISM HAVING A NORMAL "OF" POSITION BALANCING PRESSURE IN SAID MOTOR AND BEING MOVABLE RELATIVELY FROM SUCH "OFF" POSITION TO ESTABLISH DIFFERENTIAL PRESSURES IN SAID MOTOR; NORMALLY SPACED ENGAGEABLE PORTIONS MOUNTED RESPECTIVELY ON THE PRESSURE-RESPONSIVE UNIT AND SAID VALVE PORTIONS FOR DEFINING THE LIMITS OF RELATIVE OPERATING MOVEMENT OF THE LATTER; THE IMPROVEMENT WHICH COMPRISES: A WORK-PERFORMING ELEMENT ACTED ON IN PART BY SAID PRESSURE-RESPONSIVE UNIT; A REACTION AND FORCE-TRANSMITTING DEVICE INCLUDING A NORMALLY RELAXED RESILIENT MEMBER HAVING LEVER-ACTION OPERABLY DISPOSED BETWEEN SAID WORK ELEMENT AND PRESSURE-RESPONSIVE UNIT IN ENGAGEMENT WITH SAID MOVABLE MEMBER; MECHANICAL MEANS FOR TRANSMITTING FORCE FROM SAID OPERATOR MEMBER TO MOVE SAID MOVABLE MEMBER TO INAUGURATE TENSION IN SAID RESILIENT MEMBER BY DEFORMING IT PRIOR TO ENERGIZATION OF SAID MOTOR WHEREBY THE LATTER WHEN ENERGIZED CAUSES THE REACTION FROM SAID WORK ELEMENT TO BE TRANSMITTED THROUGH SAID RESILIENT MEMBER UNDER INCREASING TENSION ON THE OPERATOR MEMBER WHILE THE PRESSURE-RESPONSIVE UNIT OPERATES THROUGH A PREDETERMINED POWER RANGE DEFINED BY MINUTE SEPARATION OF THE WORK ELEMENT AND PRESSURE-RESPONSIVE UNIT INDUCED WHEN PLACING SAID RESILIENT MEMBER UNDER TENSION AS AFORESAID; A LINK FOR TRANSMITTING FORCE FROM SAID OPERATOR MEMBER TO MOVE ONE OF THE VALVE PORTIONS RELATIVELY WITH RESPECT TO THE OTHER PORTION FROM "OFF" POSITION; AND A NORMALLY PRELOADED SPRING OPERABLY REACTING BETWEEN SAID VALVE PORTIONS FOR BIASING THEM APART AND ACCOMMODATING THEIR MOVEMENT TOWARD EACH OTHER FROM "OFF" POSITION UNDER INFLUENCE OF SAID OPERATOR MEMBER OPERATED FROM RELEASED POSITION. 